1. Field of the Invention
The present invention relates to refrigeration systems, particularly refrigeration systems that use hydrocarbon refrigerants and means for venting hydrocarbon refrigerant leaks.
2. Description of the Related Art
Refrigerators commonly include an insulated cabinet, the interior of which is cooled by a cooling system. The cooling system is typically disposed within a housing, which is located beneath or behind the cabinet. The cooling system generally includes a compressor; a condenser fluidly connected to the compressor; and an evaporator fluidly connected to both the compressor and the condenser and in thermal communication with the interior of the cabinet. In operation, a refrigerant gas enters the compressor where it is compressed under high pressure. The compressed refrigerant gas then flows to the condenser where it is cooled in a series of coils and is condensed into a liquid. The liquid refrigerant then flows to the evaporator where the liquid refrigerant absorbs heat from the interior of the cabinet, thereby cooling the interior and converting the refrigerant liquid back to a gas. The refrigerant gas then flows back to the compressor where the cycle is repeated. A fan is typically incorporated in the cooling system to cool the compressor and force air through the condenser coils.
An effective refrigerant should be capable of readily evaporating at low temperatures and compressing at high pressure without decomposing. Consequently, compounds that are ideal for use as refrigerants are stable compounds having low evaporation temperatures. In the past, CFCs (chlorofluorocarbons) have been used as refrigerants. However, it is believed that CFCs are harmful to the environment and, as a result, hydrocarbon refrigerants, such as propane and isobutanes, have been used in place of CFCs. Unfortunately, hydrocarbon refrigerants have a Low Flammability Limit, which means that even a small hydrocarbon refrigerant leak in the housing could result in a build up of hydrocarbon refrigerant to a concentration level above the Low Flammability Limit. A concentration of hydrocarbon refrigerant above the Low Flammability Limit is sufficient to trigger an explosion in the presence of oxygen and a flame or spark.
Hydrocarbon refrigerant leaks are, to some degree, flushed from the housing by the fan. The fan, often referred to as the condenser blower, is typically located behind the condenser near the back of the housing. The fan is typically positioned such that its axis is perpendicular to the back of the housing. The fan draws air in through the front of the housing, over the condenser coils and out through the back of the housing. This airflow path may not reach the compressor and, thus, may not sufficiently cool the compressor. In addition, the air flows perpendicular to the back of the housing such that, when the air reaches the building wall behind the refrigeration system, it is deflected in both the upward and downward directions. The air that is forced upward flows up above the cabinet and ultimately mixes with the ambient air above the cabinet. However, the air that is forced downward flows beneath the housing and back to the front of the housing, where it may then be drawn back into the housing. Consequently, any hydrocarbon refrigerant contained within this air is re-circulated back into the housing, thereby permitting the accumulation of hydrocarbon refrigerant, possibly to a level above the Low Flammability Limit.
Attempts have been made to prevent hydrocarbon refrigerant leaks by reducing the number of joints in the condenser, where leaks are most likely to occur. In addition, the operating pressure may be reduced in an effort to prevent hydrocarbon refrigerant leaks. Attempts have also been made to develop systems for detecting hydrocarbon refrigerant leaks. Such systems may monitor the thermal dynamic parameters of the system and/or the electrical consumption of the compressor, or may sense the molecules of hydrocarbon refrigerant in the air. Despite these attempts, a need remains for a system that ventilates the cooling system area to effectively flush, dissipate and dilute hydrocarbon refrigerant leaks from the housing.